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Will an indirect work for me?

I currently have an oil boiler w/ tankless coil(rated @ 6gpm).  I have a 5 story multifam with 5 lowflow showers and 10 occupants.  I typically consume 400 gallons/day in water. 

Frequently, I have family/guests and my consumption is significantly higher.  For example, I used 1500 gallons on christmas eve.  (Everyone in my building seemed to have guests staying for the holidays).  In one 6 hr period, I used 750 gallons. 


I realize that tankless coils are ineffecient and what not, but it does provide virtually endless hot water.   Would an indirect be able to keep up with my peak demand?


  • Zman
    Zman Member Posts: 7,467

    An indirect would work great for you. If you have the BTU's to run a tankless you can absolutely do an indirect. The indirect will also work in the future whenever you upgrade your boiler.

    If you plan on keeping your existing boiler for a long period of time you can use your existing tankless coil with an electric water heater for storage (no electric hooked up). Icesailor has posted a proven detail for this.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • SWEI
    SWEI Member Posts: 7,356
    edited February 2013
    400 gallons per day

    of water, gotcha.  Indirect will be great.

    Get a proper demand calc done, and consider gifting your tenants with new showerheads.  Seriously.
  • mark schofield
    mark schofield Member Posts: 152

    The local water co. on the CT. shoreline gives water saving kits which include inserts for sink aerators, a dye for toilets, an expandable bladder for the toilet tank,and as SWEI said, water saving shower heads.
  • kcopp
    kcopp Member Posts: 4,257
    edited February 2013
    If people don't....

    pay... they wont conserve. I would look into installing 1.6 g/Flush toilet and 40g electric water heaters for each unit. Each tank is powered by each units electric panel.  That way everyone pays for their own hot water at least...
  • anton_2
    anton_2 Member Posts: 2
    Folks seem to be implying that i'm using too much water.

    I've done as much as I can to reduce consumption.  I've replaced the old 5.5 gpm shower heads with low flow one.  3/5 toilets are Toto low flow models.   I used to consume 250 HCF per year.  Now I'm below 175 HCF per year. 

    I mentioned that I like the tankless because it gives me virtually endless hot water and realize this comes at a price.  When it comes to actually sizing an indirect, should I be looking at 1st Hr Rating or Continuous Draw?
  • Zman
    Zman Member Posts: 7,467

    What size is your boiler?

    There are 2 factors, storage and heat exchanger size.On one hand you don't need much storage as your boiler seems to be able to handle your needs on demand. Using this approach you could size the exchanger a bit bigger than your boiler and you would be all set.

    The other thing to consider is that your existing boiler is likely oversized for your heating needs. When you do upgrade your boiler It will likely be smaller. With a smaller boiler you will need more storage and less exchanger..

    If you post your boiler BTU rating along with the building footage type of construction and area of the country we should be able to take a guess at a good long term plan.

    Be weary of the ratings of indirects. They assume a certain boiler output and cold water temp. They may or may not apply

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
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